Digestion of fibrous material



T. L. DUNBAR Filed Aug. l, 1929 Nov. l1, 1930.

DIGEsTIoN oF FIBRoUs MATERIAL um@ EEN mi@ RS .K339i wb,

Patented Nov. 1l,` 1930 PATENT OFFICE THOIAS LEONIDAS DUNBAB, OF'WATEBTOWN, NEW YORK DIGESTION OF FIBBOUS MATERIAL application mea august 1, 1929. serial no. 382,802.

The present invention pertains to the c ooking of fibrous material, and more especially to the packing of wood chips or the like, into digesters, while pre-cooking such fibrous material.

Prior to this invention, proposals have been made for utilizing hot waste liquor from blow pits, storage tanks and the like for assisting in packing chips in digesters, and for preconditioning such chips. In these pronosals, a great amount of heat 1s lost from the Waste liquor before it is used for. packing purposes, and the primary obJect of the present invention is to eliminate such waste.

This is accomplished mainly by introducing side relief liquor and/or hi h pressure gas from o'ne or more digesters irectly into the upper portion of another digester, while the latter is bein filled with chips.

With the oregoing object outlined, van with other objects in view which will appear as the description proceeds, the invention consists in the novel features hereinafter described in detail, illustrated in the accompanying drawing, and more. particularly pointed out in the appended claims. n

The accompanying drawing shows a dlagrammatic view of a suitable apparatus for use in carrying out m method.

In this drawing, t e digesters Nos. 1, 2 and 3 are connected by the usual valved side relief and high pressure gas relief branches 4, with a relief line 5, which is provided with a. control valve 6, and leads to the bottom of an accumulator 7, in which acid liquor may be preheated and pre-conditioned for use in the digester.

A low pressure gas relief line 8 is connected by valved branches 9 to the upper ends of the digesters, and this line also leads gases and vapors from the tops of the digesters into the bottom of the accumulator. The cold acid liquor may be introduced into the top of the accumulator through a conduit 10, and in the accumulator, this liquor will absorb the gases and be' preheated and pre-conditioned by the material received from the lines 5 and 8.

In accordance with the present invention, 50 whenever one of the digesters is being lled with chips or the like, side relief liquor and/or high pressure gas from one or more of the other digesters may be fed through the pipe 5, directly to the digester undergoing lilling, instead of being led to the accumulator. In accordance with my method of operating, we will assume that N o. 2 digester is on the .side relief period of the cooking operation, that is, it has just recently been illed, and its side relief branch 4 is opened, so that the usual liquor is iowing ott' through the side relief. Instead of sendlng this liquor back into the accumulator, as has heretofore been the practice,I shut the valve 6 and o en the valve in the side relief branch 4 of `gester No. 3, then as the chips fall into No. 3 di' gester, which is being filled', the side relief liquor coming from digester N o. 2 flows in on top of these chips, and packs the chips more evenly in the digester. This also, in addition to packing the chips, conditions them, as the liquor coming from No. 2 digester is hot, and this hot liquor flowin into No. 3 digester, as the same is bein lille starts penetrating the chips, as they all into the digester, and by giving all the chips very nearly the same hot moisture content, in reality actually starts the cooking process.`

As No. 3 is filling with chips hot high pres sure gas from digester No. l may also be added to the hot liquor flowing through the side relief branch 4 of No. 3. Consequently, the side relief liquor packs the chips in digester No. 3 and partially conditions them. In addition, the high pressure gas going into the digester and meeting the flowing stream of chips which is falling into this digester, has the effect of penetrating the chips due to absorption, so that the chips not only absorb liquor but also some SO2 gas. This initiates the digestion process.

At this point I wish it to be particularly noted that in accordance with my invention, no additional apparatus is necessary for the storage of hot liquor, as I utilize the already existing side relief branch, and simply How the hot liquor and hot gas through the same from one or more digesters on the side or high pressure relief, into another digester that is undergoing filling. e

This method saves considerable on the cooking period, as by the time the digester .1s filled, the chips have already taken up considerable hot liquor and gas. As vsoon as digester No. 3

5 is filled withI chips, the valve in its side rel1ef branch is closed, and the valve 6 is again opened, so that an further side relief from digester No. 2 or high pressure relief from No. 1 will now go directly into the accumulator for use in pre-heating and pre-conditioning the v acid liquor therein. Furthermore, as soon as digester No. 3 is filled with chips in the manner above explained, acid from the accumulator is forced into the bottom 'of this digester by means of a pump 11 that is interposed in a feed pipe 12 which is connected to the bottoms of the digesters by means of valved branches 13. The acid is pumped into digester No. 3 until the samev is completely filled with chips, and liquor. Then the cooking of this digester proceeds 1n the normal manner, except that due to the fact that hot relief liquor and gas werev run into this digester during the filling, and the further fact that hot acid was pumped from the accumulator into the digester, very little steam is required at the start of the cook.

It will be understood that the hot side relief liquor and high pressure gas are used in the filling of any one of the digesters, and that my improvements, while shown for use with a battery of three diges'ters, may be employed with any number of digesters.

In accordance with my present invention, I'have not only provided .a system for effectively absorbing the gases relieved fromithe digesters, and for utilizing thev heat units thereof, but have furnished a method whereby the chips are not only initially pre-conditioned during the lling of the digester, but are in effect pre-cooked before any steam is turned into the digester.

It is manifest that various changes may be made in the details disclosed, without departing from the spirit of the invention, as eX- pressed in the claims. p What I claim and desire to secure by Letters Patent is 1. In the digestion of fibrous material, fiowing side relief liquor from a digester undergoing cooking, directly into a digester undergoing filling, and utilizing said side relief liquor for packing chips evenly in a digester.'

2. In the digestion of fibrous material with acid liquor, releasing hot acid liquor-and gas from digesting means and flowing the same directly into the upper portion of another digester while filling the latter with fibrous material.

3. In the digestion of fibrous material with acid liquor, utilizing hot acid fluid from digesting means for packing fibrous material e5 into a second' digester, and afterwards forc- `into the second digester to completely fill ing hot pre-conditioned acid liquor into the second d1gester.

4. In the digestion of fibrous material, flowing hot acid liquor from a digester intoa second digester undergoing filling, and causing said hot acid liquor to pack the fibrous material in the second digester, cutting off the flow of hot acid liquor from the first` digester to the second digester and then forcing hot acid liquor from an extraneous source the latterwith fibrous material and acid liquor.

5. In the digestion of fibrous material, owin hot acid liquor from the upper por` tion o a digester undergoing cooking, directly into the upper portion of a second digester while the latter is being filled with brous material, cutting off the flow 'of acid liquor from the first to the second digester after the desired amount of fibrous material has been placed in the second digester, and then forcing hot acid liquor from an -extraneous source into the second digester to completely fill the latter with fibrous material and het acid liquor.v

6. In a method of the character described, cooking fibrous material with acid liquor in a digester, flowing side relief hot liquor from said digester into acid liquor contained in an accumulator, cutting ofi' the flow of side relief Iliquor from the digester to the accumulator, and then flowing said side relief liquor directly into the upper portion of a second diester, while the latter is being charged with 100 brous material, cutting off the flow of side relief liquor from the first to the second dipletely fill the latter with fibrous material and hot acid liquor.

7. In a method of the character described, digesting fibrous material with acidliquor ina closed digester, passing side relief liquor from said digester into acid liquor contained in an 11o accumulator, cutting ofi' the flow of side relief liquor from the digester to the accumulator, and flowing this side relief liquor directly from the digester to a second digester while the latter is bein filled with fibrous material, cutting off' the ow of the side relief liquor from the first to the second digester and returning said flow to the laccumulator, then forcing hot acid liquor from "the accumulator into the second digester chamber to completely-fill the latter with fibrous material and acid liquor, and passing top relief gas from the first digester into the accumulator for pre-conditioning and pre-heating the acid liquor contained there1n.

8. In the digestion of fibrous material, utilizing gases, vapors and liquor released from digesters undergoing cooking for preheating and pre-conditioning acid liquor in an accumulator, flowing hot acid liquor from 130 one digcster directly into another di ester While the latter is being filled with rous material, cutting ol the iow of acid liquor to the last mentioned digester after a predetermined mass of librous material has been deposited therein, and then forcing hot acid liquor from the accumulator into the last mentioned digester to completely lill the latter with fibrous material and acid liquor.

. 9. In a system of the character described feeding fibrous material into the top of a digester, and flowing hot acid liquor from the upper portion o a digester undergoing cooking, directly into the upper portion of the digester undergoing filling, and utilizing said hot acid liquor for packing fibrous material in the last mentioned digester While the latter is being filled.

In testimony whereof, I have signed this specification.

. THOMAS LEONIDAS DUNBAR. 

